Addition agents for improving electrophoretic deposition of aluminum from organic suspensions



United States hastens 3 067 120 ADD ITION AGENTS fiORdMPROVlNG ELEC'KRU- PHGRETIC DEPUSITIUN F ALUMINUM FR-GM ORGANIC SUPENIUN tion of each, consisting of about one half the original charge, may then be collected and used as the suspending media.

The electrophoretic apparatus, per se, forms no part of acetate. These liquids may be distilled after drying over anhydrous sodium sulfate, for example. The middle frac- Fred Pearlstein, Phiiadelphia, Pa, assignor to the United 5 the invention, but may suitably partake of inch metal States of America as represented by the Secretary of rods plated with about 0.002 inch of gold and conveniently the y spaced approximately 0.175 inch apart.

N0 g gif i zf w 3 55349 In evaluating the effectiveness of the addition agents fl. of the present invention, electrophoretic tests were con- (Granted under (jade (1952) 10 ducted on the aluminum suspension with and without the The invention described herein may be manufactured incorporation of the agents. The aluminum fla w and used by or for the Government for overnm nt l mixed into each of the collected organic media to provide purposes Without the payment to me of any royalty a mixture containing about 0.1 to by weight-volume thereon, of aluminum. The mixture was vigorously shaken before This invention relates to the electrophoretic deposition 5 insefiing the 616600668 thefeinio- Field Strengths rangof aluminum from organic solvents and more particularly ii'lg hem/$511 about 12 t0 Volts P Centimeter of P- concerns addition agents thereto for improving the quality oration of electrodes were then applied for specified of such deposits. periods of time. In all cases, where no addition agents Electrophoretic deposits of aluminum are normally were mp y deposits, if y were formed, Were produced from non-aqueous liquids, since the formation 20 either y y, Hen-uniform, had little Cohesive of gaseous products from aqueous suspensions interfere strength, or were produced so slowly as to be unfeasible. with the uniform deposition of the metal. In the past, In accordance with the invention, additions of n-butylthese deposits have been characterized by high porosity amine in concentrations of 0.02 to 10% by volume were and mechanical weakness. Further, the deposition rates found to yield good electrophoretic deposits of aluminum. were quite low or the solvent used in suspending the Minor additions of suitable binders, such, forexample, aluminum flakes or finely comminuted aluminum powder as rosin, gum benzoin and ethyl cellulose were effective were malodorous. to produce more cohesive deposits.

It is, therefore, a principal object of this invention to Although it is not intended that the invention be limited provide a suitable bath solution for the successful electrothereto, there is set forth hereinbelow for purposes of il- "Ifioretic depositing of aluminum which overcomes, at lustration, examples of values which may suitably be least in part, the aforementioned physical defects. employed in practicing this invention:

Preferred Preferred Preferred addition wt. v01. volts/cm. Current Deposition Organic Liquid n-butylpercent of separation Density, Rate, Remarks amine, vol. aluminum of eleema./cm. mm./min.

percent flake trodes Acetone 0.2 4 100 0.15 1.1 HilghtDeposition Chloroform 0.2 4 300 0.01 0.66 Cohisfiye de- Methyl Acetate 0.2 4 100 0.10 0.28 Hig fi throwing power.

Another object of the invention is to provide addition It has been found that minor additions of other agents for incorporation with non-aqueous solvents whereamines, such as isopropylarnine, tributylamine, aniline, in aluminum may be easily and rapidly electrophoretically and ot-naphthylamine, in proportions generally similar to deposited. the n-butylamine tabulated above, yield satisfactory elec- The exact nature of this invention as well as other trophoretic deposits of aluminum when suspended in aceobjects and advantages thereof will be readily apparent tone.

from consideration of the following specification: From the foregoing description, it is apparent that the Briefly, the present invention is based on the discovery electrophoretic deposition of aluminum from selected nonthat by incorporating certain organic substances, as deaqueous suspending media has been provided by means scribed more fully hereinafter, into a suitable non-aqueous of minor additions of commercially available organic aluminum suspension, the electrophoretic deposition of the solvents to such media, and wherein the aluminum is aluminum can be materially improved as compared with more uniformly, more rapidly, and more coherently deheretofore used compositions. posited. y

In preparing the novel compositions embodied herein, I claim:

the components thereof may be simply blended to provide 1. A bath composition for electrophoretically deposita uniform suspension using agitation and/or other suiting aluminum flake material and finely divided aluminum able means. In a preferred embodiment, the aluminum 0 from non-aqueous suspensions thereof consisting of about powder used was a flake material having a particle size 0.1 to 20% weight-volume of said aluminum dispersed less than 44 microns, and was removed of most stearic in an organic solvent selected from the group consisting acid and other organic contamination by dispersing it in of acetone, chloroform and methyl acetate and a minor warm acetone, filtering through a Buchner funnel and reproportion of n-butylamine in the proportion of about peating the process several times. The final filter cake is 55 0.02 to 10% by volume of the entire suspension.

then dried. It is to be understod that the invention is not 2. A bath composition for electrophoretically depositing intended to be limited to aluminum flake material, and aluminum flake material and finely divided aluminum other finely divided aluminum may be used satisfactorily. from non-aqueous suspensions thereof consisting of about The organic solvents to be employed in the compositions 0.1 to 20% weight-volume of said aluminum dispersed in contemplated herein are acetone, chloroform and methyl an organic solvent selected from the group consisting of acetone, chloroform and methyl acetate and a minor proportion of an amine selected from the group consisting Patented Dec. 4, 1962 3 of isopropylamine, tributylamine, aniline and alpha naphthylamine in the proportion of about 0.02 to 10% by volume of the entire suspension.

3. The composition of claim 1 further characterized by said aluminum being of a particle size under 44 microns.

4. The composition of claim 1 wherein said aluminum comprises about 4% by weight-volume of the entire suspension and the n-butylamine comprises about 2% by volume of the entire suspension.

References Citerl in the file of this patent UNITED STATES PATENTS 2,462,125 Oakes Feb. 22, 1949 OTHER REFERENCES Blue et al.: The Electrochemical Society, Reprint 65 2, April 30, 1934, pages 25-38.

De Boer et al.: Electrodeposition of a Thin Layer of 10 Powdered Substances, Rec. Trav. Chim., volume 58,

1939, pages 662-5.

Wood et al.: Journal of the Electrochemical Society, January 1957, pages 2936 

1.A BATH COMPOSITION FOR ELECTROPHORETICALLY DEPOSITING ALUMINUM FLAKE MATERIAL AND FINELY DIVIDED ALUMINUM FROM NON-AQUEOUS SUPENSIONS THEREOF CONSISTING OF ABOUT 0.1 TO 20% WEIGHT-VOLUME OF SAID ALUMINUM DISPERSED IN AN ORGANIC SOLVENT SELECTED FROM THE GROUP CONSISTING OF ACETONE, CHLOROFORM AND METHYL ACETATE AND A MINOR PROPORTION OF N-BUTYLAMINE IN THE PROPORTION OF ABOUT 0.0I TO 10% BY VOLUME OF THE ENTIRE SUSPENSISON. 